1. Field of the Invention
The present invention is usable in coordinate measuring machines, such as a three-dimensional measuring machine with regard to a touch signal probe which outputs touch signals by contact with an object to be measured.
2. Description of the Related Art
The touch signal probe is attached to the probe installation shaft which moves the probe into contact with an object to be measured placed on a mounting table of the measuring machine. When the stylus of the touch signal probe touches the object to be measured, since the position of the stylus installation shaft is determined by sensors, the sensors output touch signals. Accordingly, the size and shape of the object to be measured can be measured based on the touch signals outputted from the sensors. The stylus installation shaft is supported to be displaced by the blade-like springs. To prevent the vibrations of the stylus generated during a movement of the probe to the objects to be measured and after a contact with the object to be measured, the stylus installation shaft is equipped with a damper mechanism filled with viscous liquid around a damper slat.
Conventional touch signal probes include one type in which one blade-like spring is used and the other type in which two blade-like springs are spaced away from each other along a longitudinal axis of the stylus installation shaft and when the stylus touches the object to be measured, according to the direction from whence they are touched, the stylus installation shaft is displayed at right angles to the longitudinal axis direction of stylus installation shaft (the X-Y direction) through the blade-like spring part, or in axial direction (the Z direction) of the stylus installation shaft.
In the touch signal probe where one blade-like spring is used, because the spring of the blade-like spring is greatly different between the X-Y direction and the Z direction, with regard to the measuring force of the blade-like spring at the time when the stylus touches the object to be measured, the measuring force in the X-Y direction is dozens of times as big as that in the Z direction, so that the problem of generating polarity of the measuring force was brought about as a result. While in the touch signal probe where two blade-like springs are used, because it is possible to make the difference between the spring constant in the X-Y direction and in the Z direction small, the difference of the measuring force between each direction can be made smaller than that of the touch signal probe having one blade-like spring but it doesn't become small enough and the problem of polarity in the measuring force has remained.
Moreover, in the touch signal probe where two blade-like springs are installed, these two blade-like springs are arranged widely apart from each other along the longitudinal axis of the stylus installation shaft and the above-mentioned sensors are provided between the two blade-like springs. Therefore, since the distance between the displacement center of the stylus installation shaft and the sensors is short, when the stylus touches the object to be measured from the X-Y direction even if the displacement quantity of the stylus is enough, the displacement quantity of the stylus installation shaft at the part where the sensor is provided is small, whereby this type evolves a problem of lowering the detection sensitivity of the sensor in the X-Y direction.
An object of the present invention is to provide a touch signal probe without the polarity of measuring force in the way of equalizing the measuring force in the X-Y direction and the Z direction.
Another object of the present invention is to provide a touch signal probe with high detection sensibility in the X-Y direction by sensors.